1. Field of the Invention
The present invention relates to a lens apparatus and a camera system.
2. Description of the Related Art
According to one known lens interchangeable type camera system, a camera body has an autofocus (“AF”) function and a focus preset function (“FP”) configured to move a focus lens to a stored position, and a lens apparatus includes a driver and a position detector of the focus lens. A current focus position (as a position of the focus lens) is transmitted from the lens apparatus to the camera body, and a target focus position or moving amount is transmitted from the camera body to the lens apparatus based upon it.
In recent years, a rear focus type lens is used in lens apparatuses compared with a front focus type lens. However, in the rear focus type lens, as a zoom position (as a position of a variable magnification lens) is changed, the focus position shifts and it is necessary to move the focus position according to the zoom position so as to focus at the same object distance. A relationship between the zoom position and the focus position is referred to as a “cam curve.”
Japanese Patent Laid-Open No. (“JP”) 2008-227799 discloses a method for performing focusing from a camera by object distance information so that an influence of changes of a focus position occurring as a result of correcting shifts of focus position generated by zooming decrease.
However, the method of JP 2008-227799 is not capable of applying to a camera which does not control focusing with focus pulses or object distance information.
Additionally, when minute amplitude wobbling is performed using pulse information, a camera is capable of performing the wobbling by pulse amounts taking into account a lens sensitivity relative to defocus amounts. However, like JP 2008-227799, when focusing is controlled by the object distance information, a problem occurs where the depth of field becomes shallower and a resolution of an object distance must be significantly increased occurs. Further, since it is necessary to transmit parameters regarding pulse information and object distance information to a camera from a lens, an increase of the amount of information transmitted is caused.